updated 07:25 pm EST, Thu November 10, 2011

Other factors may be complicating the issue

Early reports on the iOS 5.0.1 update indicate that the update doesn't fully resolve the battery life issues on the iPhone 4S seen by some users, though a minority are reporting that the update did indeed fix the problem. Because the update is so new, users in Apple's support forums and elsewhere are still methodically going through possible other causes for battery drain, but for some the update changed nothing in terms of useful battery life.

The battery drain issue appears to be a problem with iPhone 4S owners only, and may in part be due to factors such as the increased use of notifications and location services in the iPhone 4S, as well as the inability to turn 3G off (other than using Airplane Mode). The iPhone 4S was also recently discovered to have an always-on proximity sensor as part of its Siri service which may also be contributing to higher battery drain.

The majority of users are saying that the update has shown no measurable improvement, though some users report significant changes, both in terms of battery use and overall speed. So far, the leading suggestions for maximizing battery life appear to involve turning off unneeded notifications and location services. There is also a "setting time zone" setting in "System Services" within Location Services that, for some users, needs to be unchecked in order to prevent the iPhone 4S from constantly polling for this information.

Others have suggested that examining the PID activity on some of the rapidly-draining iPhones may show a constantly-crashing system service that could be the true culprit. A complete power-down and reset appears to resolve that issue. In either case, a number of users are reporting excessive battery drain that could be an indicator of another issue, compared to the majority of reports that complain of only slightly faster battery drain that was seen with the iPhone 4.